OPERA Die Aegyptische Helena Garsington

This is the opera with the omniscient mussel, the conch that knows everything. Since its premier in Dresden in 1928, Die Aegyptische Helena has never been staged in Britain. Perhaps that entry on the cast list (contralto) did not help? Sixty nine years later, it is presented on the open-air stage at Garsington Manor (with a side view of giant blue hollyhocks) and revealed as a fascinating, hugely enjoyable work. It is a sign of the seriousness and the success of the production that the mussel made sense: instead of being embarrassed by it (as Strauss was), David Fielding made it central. A big shell sat on stage and later functioned as the vessel for the two potions of forgetfulness and remembrance.

The role was sung extremely well by Rebecca de Pont Davies, a visually arresting figure swathed, wigged and made-up in black, as Aithra's shadow, her inner voice. Aithra's husband Poseidon went and came at the start and end of the opera to illuminate Aithra's story, even if Hofmansthal omitted these events from his crowded libretto. Aithra was sung by Helen Field who, on the evidence of this and her recent, unexpected, Salome at Convent Garden, has turned into a radiantly expressive soprano, with immaculate tone and burnished, tireless top notes. She is also a considerable actress, making every syllable of the German meaningful. If she has one weakness, it is that she makes it all sound easy. Fielding made it look easy in that Die Aegyptische Helena, like so many Strauss operas, turns out to be about marriage: Aithra intervenes in the troubled marriage of Helen and Menelaus, using magic to help them forget the past. The couple learn instead to remember and, as it were, work through their past. At the end, their child is suddenly on hand to ask, "Where is my beautiful mother?' and the family is reconstituted. Aaaaah.

Susan Bullock brought out the woman inside the myth and made Helen of Troy believable as well as glamorous, sympathetic, even funny, when Arabs threw themselves at her feet, proffering briefcases full of unseen treasure. In a nice touch, the briefcases were lined up along the front, just as the ramparts of Troy were evoked. John Horton Murray surmounted the vocal challenges of Menelaus with aplomb. It is one of Strauss's most impossible tenor roles: if only this singer could learn or bother to act, he would be assured of a major career on stage.

Casting is one of Garsington's major strengths: Roderick Earle as Altair, Nicholas Sears as Da-ud, both servants (Yvette Bonner and Helen Astrid) and the Elves all distinguished themselves. With a reduced orchestra, the conductor Elgar Howarth wisely went for articulation and clarity. Some of the score's sumptuousness emerged after the interval, when the pit's protective roof was removed, to reveal expert playing from the brass. The rest will have to wait for another production, this time inside an opera house, please, soon.

Further performances: 24, 28, 30 June; 3, 6 July